The object of this grant is to determine the immunoregulatory function(s) of a solube helper factor(s), which is involved in the generation of cytotoxic T (thymus derived) lymphocytes that are directed against allogeneic cells and syngeneic tumors. To accomplish this, we are seeking to identify certain biological, biochemical and functional properties of this helper factor, and to determin its relationship to other immunoregulatory molecules (i.e., T cell growth factor, lymphocyte activating factor, interferon).